Victoreen Model 6000-200 and 500-200
High Sensitivity 10 cc CT Ion Chamber
High sensitivity CT chamber designed for multislice scanners
10 cc volume over 10 cm length chamber
Calibrated in units of R•cm/Coulomb
Diagnostic X-ray
6000-200 and 500-200
INTRODUCTION
Victoreen’s High Sensitivity 10 cc CT Chamber consists of a pencil-type ionization
chamber with sensitive length of 10 cm for computed tomography (CT) Quality
Assurance. This high sensitivity 10cc CT chamber has three times the sensitivity
of a standard 3.2 cc CT chamber and is designed to be used with your existing CT
phantoms. This new architecture provides more stable, reproducible dose
measurements for CT slices from 1 mm to 1 cm in thickness.
The 6000-200 probe has a 0.9 meter flexible low noise cable which is terminated
in a male coax BNC connector for signal and a banana plug for bias. It is designed
for use with the Model 8000 NEROTM mAx, 4000M+, NEROTM or RAD CHECKTM
PLUS.
The 500-200 probe has a 0.9 meter flexible low noise triax cable which is terminated
in a male triax BNC connector, and is designed for use with the Model 530, Model
35040, and other electrometer/dosimeters. Calibration is stated in terms of R•cm/nC.
APPLICATIONS
It has been shown* that in a phantom, integration of the radiation exposure profile
produced by a single scan from a CT scanner along a line normal to the slice,
divided by the table increment, is equal to the exposure to a central slice at that
point produced by a series of scans. The line of integration must be of sufficient
length to intercept not only the primary beam, but also the Compton scatter produced
in the phantom. This integral is then expressed as R•cm.
A long, thin radiation probe can be used to make this measurement. The probe
may be calibrated in a uniform field covering its entire length, generating a
correction factor in the conventional manner. Subsequent probe readings, when
multiplied by the conventional correction factor, and then by the probe’s sensitive
length, will be in units of R•cm.
Since the Victoreen 6000-200 and 500-200 probes are intended mainly to be used
to integrate radiation exposure profiles produced by the CT scanners, this length
(10 cm) factor has, for the user’s convenience, been built into the calibration.
Thus, the correction factor provided is stated in terms of R•cm/Coulomb.
FEATURES
• The Model 6000-200 and 500-200
High Sensitivity CT Ion Chambers
were designed for multislice scanners
but still fit into the conventional CT
phantoms (see CT Dose Phantoms) for
calculation of Computed Tomography
Dose Index (CTDI) and for CT Quality
Assurance
• The 10 cc volume and 10 cm length
make this chamber ideal for spiral/
helical and conventional CT machines
SPECIFICATIONS
Detector Type Vented air ion chamber
Volume 10.1 cc
Sensitive Length 10.0 cm
Chamber Material Acrylic (PMMA)
Chamber Outside Diameter 0.5 in (12.7 mm)
Chamber Inside Diameter 0.45 in (11.44 mm)
Chamber Wall Thickness 77 mg/cm2
Electrode Material Aluminum, 1100
Sensitivity3.2 R•cm/nC (nominal) or 0.3/nC
Standard Calibration
100 kVCP, 5.5 mm Al HVL (NIST Tech. M100)
Typical Energy Dependence
Response Uniformity Along Axis
± 3% over central 90% of active length
Beam Orientation Normal to chamber axis
Leakage Current
(300 V collection potential) Less than 10-14 A at
10 min polarization time
Intensity Limits, 6000-200/500-200
Continuous beam: 31.6 R/sec
(1% recombination loss)
Pulsed Beam 15.8 mR/pulse (1% recombination loss)
Collection Time 0.478 mSec
Cable Length 3 ft (0.9 m)
Operating Voltage -3 00 V
Termination
Model 6000-200 Coax BNC for signal & banana
plug for bias
Model 500-200 Triax BNC
CT Dose Phantoms
These CT dose phantoms were designed for use
with standard CT ion chambers such as
mentioned above, in accordance with the Food
and Drug Administration’s performance standard
for diagnostic X-ray systems, which includes
regulations specifically applicable to CT systems
(21 CFR 1020.33). These phantoms allow the
user to calibrate CTDI and dose profiles:
Model 76-414 Head Dose Phantom, with 5 plugs
Model 76-415 Body Dose Phantom, with 5 plugs
Model 89-414 Carrying Case
PHANTOM SPECIFICATIONS
Material Acrylic (PMMA)
Thickness 5.94 in (15 cm)
Diameter Head Dose 6.30 in (16 cm)
Diameter Body Dose 12.59 in (32 cm)
Arrangement
One on center & four around periphery, 90° apart,
1 cm from edge
Inside Hole Diameter (for plugs or probe)
0.515 in (1.31 cm)
Hole Plugs 5 Acrylic
Length 5.94 in (15 cm)
Diameter 0.500 in (1.3 cm)
Other Phantoms Avalilable for CT Quality Assurance
Model 76-410 Series, CT Performance Phantom
Model 76-430 Mini CT QC Phantom
Model 76-409 Spiral/Helical CT Lesion
Detectability Phantom
Model 76-432 CT Spiral Phantom
Model 76-412 CT-SSP (Slice Sensitivity Profile)
Point Response Phantom
Model 84-357 Interventional Triple-Modality
3-D Abdominal Phantom
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